Caryomyia tubicola (Osten Sacken)

Cecidomyia tubicola Osten Sacken 1862: 192; Felt 1909:293 (Caryomyia).

Hosts: Carya glabra, laciniosa, texana, pallida, tomentosa, ovata, cordiformis

Gall (Figs. 26, 74-77).— Common and widespread (Map 1) on Eucarya hickories and occasional on C. cordiformis of Apocarya section; found singly or in groups; 3-7 mm in height, on lower leaf, usually between veins, occasionally adjacent to a vein; elongate-cylindrical, usually erect, knurled at apex; shiny, with minute longitudinal ridges; green, yellow, brown, or black; base of tube abruptly conical, deeply set into, and tightly sheathed by thick, scabrous, leaf growth with sharp apical edge; larval chamber variable in length, occupying basal half to nearly entire length of tube, lateral walls thin, hard, firm, with longitudinal ridges; distal part of cylinder not hollow, traversed from larval chamber to apex by thin fibrous bundle. This gall superficially resembles that of C. subulata but the shape of the base is different, that of C. subulata being deeply recessed rather than conical. The long shaft of both galls set them apart from other Caryomyia galls, but conical bases and leaf sheaths are also seen in galls of C. melicrustum and C. striolacrustum.

Affinities. — The closest relative of this species is not apparent, but galls of C. melicrustum and C. striolacrustum also have conical bases that are set into a socket made by the surrounding leaf.

Biological notes. — This may be the most common species of Caryomyia. While tubes of mature galls are usually about four times as long as wide, many are much shorter. Larval success does not appear to depend on gall length. In the Washing- ton, DC area, adults emerge beginning the first week of April from galls collected the previous autumn. Pupae emerge from a weak area at the base of the tube that was scraped away by the larva in the previous season (Fig. 77). New galls are visible by mid-May as a thickening visible on both surfaces of the leaflets, but they are still green and the tube has not yet begun to elongate (Fig. 74). Additional, apparently new galls can be found through early August. First instars are translucent and elliptical and lie flat against what will become the base of the tube. As the gall grows, the exterior is quite hard but the base, hid- den in the enveloping leaf collar, is initially soft until it grows to enclose the first instar. The larva then becomes more evenly cylindrical and mi- grates up the lengthening tube. By late May some tubes have begun to emerge from the basal boot. By mid-June some of the tubes have achieved their full length and the larvae have mostly molted to the more cylindrical second instar. By mid-July some galls contain third instars. The tubes mostly dehisce from the leaves before leaf drop. This species is one of the few that occurs on both the Eucarya and Apocarya sections, although to date I have found it only on C. cordiformis of the Apocarya group. Galls on C. cordiformis are never so common, dense, or robust as those on the Eu- carya group, but more weak-walled galls may be a function of the thinner leaves of C. cordiformis. On C. cordiformis the galls are usually found along a vein.

Range: AL, AR, CT, FL, GA, IL, IN, KY, LA, ME, MD, MA, MS, MO, NH, NJ, NY, NC, OK, Ontario, PA, SC, TN, TX, VA, DC, WV

Caryomyia tubicola [new combination]

Caryomyia n. g.

Type Cecidomyia tubicola

Cecidomyia tubicola
Hormomyia tubicola

Caryomyia tubicola

Carya sp.
Cylindric leaf galls
Greenish or black, cylindric, length 4 to 5 mm, diameter 1 mm.

Gall elongate-tubular, green to brown, set in socket on leaflet and readily detachable... Caryomyia tubicola (Osten Sacken)